Calendar data is often maintained in a server calendar data store on a calendar data server computer system. A client computer system may also maintain a client version of the calendar data in a client calendar data store. The client version may be version of the entire calendar data from the server or the client version may be a subset of the calendar data from the server. Such systems can allow the calendar data on the client to be synchronized with the calendar data on the server. To do this, the calendar data can be sent from the server to the client. The synchronization data may include data for a recurring calendar item. For example, the data may include a master record for the recurring item.